MESOSCALE PRECIPITATION DISCUSSION 0214
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1101 AM EDT FRI MAY 12 2017

AREAS AFFECTED...PORTIONS OF AR, WESTERN TN, & NORTHERN MS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 121500Z - 122100Z

SUMMARY...A CYCLONE IS EXPECTED TO LEAD TO SHORT CONVECTIVE BANDS
AROUND ITS PERIPHERY, WITH SOME STORMS SHOWING LITTLE MOTION NEAR
ITS CENTER.  HOURLY RAIN RATES UP TO 1.5", WITH LOCAL AMOUNTS OF
2-3", COULD LEAD TO FLASH FLOODING.

DISCUSSION...A DEEP-LAYERED SURFACE LOW WHICH IS NOT QUITE
STACKED, IS LOCATED ACROSS WESTERN AND CENTRAL AR AND MOVING
SOUTHEASTWARD.  PRECIPITABLE WATER VALUES OF 1.2-1.5" EXIST IN ITS
VICINITY PER RECENT GPS DATA AND 12Z INFORMATION FROM THE LITTLE
ROCK AR/LZK SOUNDING.  MLCAPES FROM AR, WHERE CIN APPEARS TO HAVE
ERODED, ARE 500+ J/KG.  BULK SHEAR IN THE 0-6 KM LAYER IS 25-45
KTS PER RECENT SPC MESOANALYSES.

SATELLITE IMAGERY SHOWS BREAKS IN THE CLOUD COVER ACROSS PORTIONS
OF AR, WESTERN MS, AND SOUTHWEST TN WHICH SHOULD ALLOW MLCAPES TO
BUILD ~1000 J/KG DURING THE DAY TODAY.  THE BUILDING INSTABILITY
SHOULD LEAD TO EXPANDING CELL COVERAGE WITH TIME.  AROUND THE
SYSTEM'S PERIPHERY, WHERE THE FLOW IS CYCLONIC AND UNIDIRECTIONAL,
SHORT PERIODS OF CELL TRAINING ARE POSSIBLE.  CLOSER TO ITS
CENTER, MINIMAL CELL MOTION IS EXPECTED. HOURLY RAIN RATES UP TO
1.5" ARE POSSIBLE CONSIDERING THE MOISTURE AND INSTABILITY
AVAILABLE.  THE MESOSCALE GUIDANCE DIFFERS IN EXACT DETAILS, BUT
PAINTS A PORTRAIT FOR LOCAL AMOUNTS IN THE 2-4" RANGE. 
CONSIDERING RECENT RAINS, FLASH FLOOD GUIDANCE IS MODEST,
PARTICULARLY IN EASTERN AR AND WESTERN TN.  FLASH FLOODING IS
POSSIBLE, PARTICULARLY IN THE SOUTHEASTERN OZARKS AND IN URBAN
AREAS. 

ROTH

ATTN...WFO...JAN...LZK...MEG...TSA...

ATTN...RFC...ABRFC...LMRFC...

LAT...LON   36009330 35969151 35898950 35028914 34088956
            33459020 33009127 33519261 34259340 35279387